Abstract
Weighting agents are mixed with the drilling mud to provide the high density required to control high-pressure high-temperature (HPHT) wells throughout the drilling operation. Solids sag occurs when the weighting agent separates from the liquid phase and settles down, causing variations in the drilling fluid density. This study evaluates barite–manganese tetroxide (Micromax) mixture to eliminate solids sag issue encountered with weighted invert emulsion drilling fluids at HPHT conditions. Micromax additive was added to barite-weighted fluids in different concentrations, 0, 15, and 30 wt% of the total weighting agent. Static and dynamic sag tests were used to evaluate the sag tendency of the new formulation under static and dynamic conditions. The performance of the new formulation was evaluated by measuring the electrical stability, density, rheological, viscoelastic, and filtration properties of the drilling fluid. The obtained results showed that Micromax additive improves drilling fluid stability by reducing the sag tendency. Adding only 30 wt% of Micromax additive eliminated barite sag issue in both dynamic and static conditions at 350 °F. 30 wt% Micromax increased the base fluid density by 5.4% and the yield point by 115% and maintained the gel strength value at 12 lb/100 ft2, while it reduced the plastic viscosity by 30%. The addition of Micromax additive improved the viscoelastic properties of the drilling fluid by maintaining a higher storage modulus to the loss modulus ratio when compared with the barite sample (in the range 4–4.5). Furthermore, 30 wt% Micromax improved the filtration performance by reducing the filtrate volume, filter cake weight, and filter cake thickness by 50%.
Highlights
Weighting agents are used to increase the density of the drilling fluid to efficiently control oil and gas well throughout the drilling operation (Caenn et al 2011; Hossain and Al-Majed 2015; Stroud 1922, 1926)
To solve the barite sag issue and the high cost of Micromax additive, compared to barite, this study evaluates the mixture of barite and Micromax to provide the required density of invert emulsion muds to drill high-pressure high-temperature (HPHT) wells effectively
The weighting agents, barite and Micromax, were characterized by measuring the elemental composition, morphology, and particle size distribution (PSD) to understand the mechanisms of sagging behavior of the solid particles and how the sag tendency can be reduced with Micromaxweighted fluids
Summary
Weighting agents are used to increase the density of the drilling fluid to efficiently control oil and gas well throughout the drilling operation (Caenn et al 2011; Hossain and Al-Majed 2015; Stroud 1922, 1926). Journal of Petroleum Exploration and Production Technology (2020) 10:2427–2435 evaluate the sag tendency of the drilling fluid is measuring the weight difference between the top and bottom of the fluid column using flow loops, sag cell setup, and viscometer sag show test (Hanson et al 1990; Aldea et al 2001; Saasen et al 2002; Temple et al 2004; Murphy et al 2008; Alabdullatif et al 2015; Davis et al 2017; Basfar et al 2018; Elkatatny 2018, 2019; Boyou et al 2019; Mohamed et al 2020) Another method of barite sag measurement is using the rheological and viscoelastic properties obtained by different rheometers and correlates the data with sag tendency (Chilingarian et al 1983; Saasen et al 1995; Power and Zamora 2003; Maxey 2007; Bern et al 2010). The effect of combined weighting agents on sag tendency and drilling fluid properties is evaluated
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